Fluid heating systems, such as hot water heating units, have been used to provide radiant heat to selected spaces. Radiators located in the spaces and tubes located in floors have been used to transfer the heat from the fluid to the air in the surrounding environment. Manually and mechanically operated valves associated with the radiators and tubes are used to control the flow of the heated fluid to the radiators and tubes thereby control the amount of heat that is transferred to the environment. Radiant floor heating systems require technical engineering design for each installation. The variations in the floors and floor coverings require alterations in the heating systems such as fluid delivery temperature and flow rates, as well as the size and spacing of the tubes that carry the heating fluid. The fluid flow controls for radiant heating systems include indoor and outdoor thermostats that control three and four way valves used to regulate the flow of fluid through boilers and heat transfer loops. The heating method and apparatus of the invention overcomes the individual design restrictions of the prior radiant heating systems.